1. Field of the Invention
The present invention relates to a laser beam printer, and more particularly to a laser beam printer for forming a toner image on a sheet in an electrophotographic method.
2. Description of Related Art
In the art of laser beam printer, measures to protect an operator from a laser beam have been developed. For example, a shutter is provided in an optical system so as to prevent leakage of the laser beam from the printer, and a safety circuit is incorporated in a driving circuit of a laser beam source so as to stop electric supply to the laser beam source when the printer is opened.
The operator's safety must be guaranteed a hundred percent at any time. Therefore further safety arrangements are required which are always effective even if the above safety devices are inoperative.